kms+pi4 without x11: 1-pixel wide bar line at left edge of screen flickers on and off once per flip

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#4,306 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
c, linux

Research direction

Start by reproducing the flickering 1-pixel bar on a Pi 4 using KMS without X11, switching from 1080p to 3840x2160 and repeatedly swapping buffers. Compare behavior with and without firmware commit 2ac4de4eaac5c1d1b25acec4a5e0a9fdb16f0c91; done means identifying the regression and confirming the display remains stable across buffer flips and mode changes.

Written by the indexing model from the issue text.

Description

with the 2ac4de4eaac5c1d1b25acec4a5e0a9fdb16f0c91 firmware, I'm occasionally seeing a 1-pixel wide line running the height of the screen, which flickers on and off with each call to swap buffers (off might = black, but I haven't tried on a white background to see if it's actually being drawn on those frames). Line is on the left edge of the screen.

if you pause swap buffer it stops toggling on and off.

this only happens about 1 out every 10 times I switch to 3840x2160 (from 1080p). If it does show up, it's there until I switch the video mode back. because it's intermittent, I haven't tested exhaustively to determine if it ever happens outside 3840, but I've yet to see it elsewhere. same binary does not exhibit this issue prior to 2ac4de4eaac5c1d1b25acec4a5e0a9fdb16f0c91.

Dominant language
C
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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